Preparation of acicular gamma-iron(III) oxide of high coercive force

US4362708A · kind A · utility

Assignee

• BASF SE

Inventors

• Manfred Ohlinger · Bischofswerda, DE
• Hans Reichert · Rheinfelden (Baden), DE
• Guenter Vaeth · Schifferstadt, DE
• Friedrich R. Faulhaber · Mutterstadt, DE
• Horst Autzen · Freinsheim, DE
• Peter Rudolf · Ludwigshafen, DE
• Joachim Werther · Bad Dürkheim, DE

Key dates

• Filing date: Nov 10, 1981
• Grant date: Dec 7, 1982
• Expiry date: Nov 10, 2001

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2006/42
• WIPO field: Audio-visual technology
• WIPO sector: Electrical engineering

Abstract

A process for the preparation of acicular gamma-iron(III) oxide of high coercive force by reducing acicular iron(III) oxide hydroxide, as it is being passed continuously through a furnace having two or more heating zones at from 190.degree. to 700.degree. C., by means of a gas mixture which is produced by passing a stream of inert gas, heated to above 250.degree. C., through an organic substance also heated to above 250.degree. C. in a vessel, and, on introduction into the furnace, is first brought into contact with the .alpha.-iron(III) oxide formed from the iron(III) oxide hydroxide by elimination of water in the first heating zone of the furnace at from 190.degree. to 250.degree. C., the .alpha.-iron(III) oxide thereby being converted to magnetite which is subsequently oxidized with an oxygen-containing gas at from 150.degree. to 400.degree. C., to give gamma-iron(III) oxide.